Optical fiber data communications systems can use dense wavelength division multiplexing (DWDM) to simultaneously transmit optical signals at different wavelengths on a single optical fiber. The optical fiber data communications systems can detect these transmitted optical signals using direct detection or coherent detection. With coherent detection, both intensity and phase of the optical signal can be used to recover information provided by the optical signals. With direct detection, only the intensity of the optical signals is used to recover the information.
An optical fiber data communications system implementing intensity modulation with direct detection can have lower power requirements, have a smaller size, and have a reduced cost in comparison with an optical fiber data communications system implementing coherent detection. However, an optical fiber data communications system implementing coherent detection can have a higher data capacity.